a) In vitro studies include an evaluation of endothelial injury using measurements of altered function such as altered permeability, modulated PGI1 synthesis, changes in endothelial cell-derived growth factor synthesis and thrombin membrane receptor number, and release of endothelial cell-specific proteins. These studies will utilize the endothelialized membrane filter technique recently developed here. b) Experimental animal studies will utilize the baboon model to examine endotoxemia, the effects of drug combinations on cannula platelet consumption and mathematical modeling of III Indium-platelet accumulation on woven Dacroh graft A-V shunts. c) In patients we propose to study platelet granular release to measure platelet activation in vivo and to determine the optimal pharmacologic regimen in the prevention of graft accumulation of III Indium-platelets.